Dental casting device and process



April 14,1925. 15 3 47 2 J. C. SHOTTON DENTAL CASTING DEVICE AND PROCESS Filed July so. 1925 A TTORNE Y3 Patented Apr. 14, 1925. v

UNITED STATES JOHN C. SHOTTON, 01 LAKEWOOD, OHIO.

DENTAL CASTING DEVICE AND PROCESS.

Application filed July 30, 1923. Serial No. 654 633.

To all whom it may concern:

Be it known that I, JOHN G. SHOTTON, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and 5 State of Oh o, have invented certain new and useful Improvementsin Dental Casting Devices and Processes, of which the following is a specification.

The present invention relates to a process of and apparatus for making dental castings, and the object of the invention is to provide a simple and efficient means whereby the molten gold or metal can be readily caused to enter the cavity of a mold. p

7 Dental castings are usually made of some precious metal, such as gold, and it has been found necessary to provide some means for forcing the molten gold to flow through the comparatively small sprue opening and enter the cavity of the mold. This has been accomplished in various ways, as by the use of centrifugal force or by means of air pressure. The centrifugal machines which have been devised for this purpose are of an expensive and complicated character, while inmany of the devices using air pressure it is diflicult to keep the air pressure under the accurate control which islnecessary to obtain satisfactory castings.

The object of the present invention has been to eliminate all of the objectionable features of the centrifugal and air pressure devices and to provide an extremely simple process and apparatus whereby the molten metal is caused to flow into the oavityof the mold under a pressure which is caused by" the generation. and expansion of gaseous mediums, so that there are no violent stresses which might rupture the mold and splendid castings can be obtained without difficulty. For a full understanding of the process and apparatus embodying the invention, reference is to be had to the following description and accompanying drawings in h h: i

Figure 1 is a side elevation --of a dental casting device which is constructed in accordance with theinvention, portions being broken away and shown in section to illus-- trate more clearly the details of construction.

Figure 2 is a top plan view of the device. Corresponding and like parts are referred to in the followingdescription and indicated on all of the views of the drawings by like reference characters.

:the metal cools and hardens.

this operation the mold is. of course, heated Referring to the drawings which illustrate one of-many possible mechanical constructions-which are adapted to be usedin practicing the invention, the numeral 1 designates a basemember upon which the mold A rests. The mold is of the usual form and includes a metal ring 2 which is filled with a suitable investment 3', in which there is a cavity 4 which has been formed by a wax pattern and which is of the exact size and shape of the desired metal casting. There is the customary depression 5 formed in the top of the investment and a comparatively small sprue opening 6 leads downwardly from the base of the depression to the cavity'. r r

The customary way of forming? these molds is to make a wax impression or pattern of the cavity in the tooth which is to receive the goldcasting. Thiswax pattern is placed upon the point of a pin by means of-which it is supported in the ring 2 while the investment 3 is poured into position. After the investment has hardened the pin is removed and the mold is subjected to a sufiicient amount of heat "to completely remove or burnout the wax, thereby leaving the cavity at and the comparatively small sprue opening ti leading downwardly thereto though so far asthe present invention is concerned the mold can be formed in any.

desired manner.

In formlng a casting a quantity of molten gold or other metal? must be placed in the depression 5-and some meansutilized for causing the molten metal to flowthrough the sprue opening 6 and enter the cavity before To facilitate so that the molten metal willnot harden when it first comes into contact therewith. According to the present invention a flared cup member 8 is utilized. said cap member being provided with a suitable handle 9. In the present instance the handle is connected to the back of the cup member by means of a stem 10 which is formed at an intermediate point in its length with an annular enlargement 11 which is useful in handling the cup member.

The cup member is partially filled with a plastic substance 12 and the mouth of the cup member is formed with an inturned fiange'13 which is of assistance in keeping the plastic substancein properposition with: in thecup member. The plastic substance. contains some material or ingredient-which, when subjected to the actionofheat, will he, volatilized or decomposed to produce a gas One form of plastic substance which canjbet used is a mixture of fullers earth and glycerine in the proper proportionsto provide a putty-like substance.

After the molten metal has been placed fin the depression 5 at the top of the heated pose the glycerine of the plastic material} to form a. gas. The air which was in ,thechamber Bis also heated and caused to expan'd a1icl ftl1e resultant pressure causedby the expansion of the heated air and the 1 05 ductionof a gas by the heating ofthe glyc erine forces the moltenmetal 7 "downwardly through thesprue opening 6 into the cavity; 4. "No" delicate or difficult manipulations are requirech:and'the. molten metal is forced downwardly into the cavit v or'the mold'lby a gaseous pressure and-without any sudden jars or violent stresses such as mighttend' 7 plastic material including air ingredient to rupture the mold. I

While I am notcertain as tolthe exact reaction or change which takes places when the glycerine is'lieated, it is probable that.

the glycerine is either vaporized without decomposition or decomposed into acrolein, (C I-LO) and. water, thereby produc n a considerable quantity ofgas Whichis unt r suflicient presure to force the molten into the mold. Any water which mayres'u-l t" from the decomposition of the mayalso be vaporized and a certain a noun't..

of steam produced thereby. Iam notjcertain as to exactly. What reaction}; if any,

takes place when the glycerine is heated:

If the glycerine is pureiit may volatilize without undergoingdecomposition, although 7 j if" it is more or'less impure. it may be par} tially or wholly decomposed, and v in tliati event it is probable that it, decomposes ac; cording to v the following, formula:

\Yhile glycerine is specifically mentioned as a substance which has given satisfactory results and can he used. it will be understood that any other substance which will produce;a g as when subjected to the heat of Ihe molten metal and mold can be used andzthatg an uothen device for forming a closed chamber over the mold can be utilized. Theproeess of forming these castings by providing a. closed chamber over the mold and then generating a gas in the closed chambeifto produce apre ssure for-forcing the molten metal *intothemoldzis zbelievedto be broa dlynew; and --it will "be understood thatl do not restri'ct nrvselfto theparticular construction shown; on the drawings or to the particular substance forgenerating a. gas in the chamber, since many modifications of the-apparatus and variations-inthe manner of' cari'ying on the process-care p0ssible' without' departing from the spirit'of" the}, invention and] within; the scope of; the claims. Theterm gas as used in'the'jclaims is i1itei1tl'(jl" l O' cover steam and' -vapors,ortheir; equivalents as wellfias the "more pcrmanentg'a seous mediumsf Having thus described my invention what;- I' claim as new andwilesire to secure by Letters Patent."is

dental casting device. including a flared(:upmember. adapted to-be fitted upon a, mold to, provide a clos ed chambeij the inclined*sides of the .cup, member enablingn it ,tov be fitted upon different "sizes of'moldsf and a plastic lining for. the cup member K which engages. the edges. oi the 'mold' toprovide a gastighujoint therewith; said.

which will be acted-upon b nthe,'heat'ofithe mold and 'moltenmetal to generate, a gas and produce a pressureto-force the moltenmetali the mold cavity,

dentalfcasting device including a flaired cup member; formed {with a substaiv tially; conically. shapedf cavity 1 and adaptedfq to fittethupon a moldfto provide a clc' 'sedq chamber, the end of the oup-"member; beingprovided with an. inwardly extending ma 'gibinalilip and 'aplastic; lining for the cup? memlier 7 which" is"; held in position by the 1 ml said-Q ii i and Which'fengages"- the edges of theimoldto pi'ovide a gasjtight jointgthers withfthei conical formation of the cavity enablingthecup member tofit l arioussizes of molds and the plastic material including- JOHN s o'rrt 

